The invention relates to a method for controlling an imaging beam path, which is tapped off from a film recording beam path of a movie camera and to an apparatus for carrying out the method.
DE 27 34 792 C2 discloses a viewfinder system for a movie camera having a rotating mirror shutter which is synchronized to the transport speed of a movie film, periodically interrupts the recording beam path, which runs from a recording objective of the movie camera to the film plane and branches off into a viewfinder beam path, such that an image of the scene to be recorded is either alternately projected onto a movie film in an exposure phase, or is diffracted from the rotating mirror shutter into the viewfinder beam path in an exposure pause. An image plane is located in the viewfinder beam path at the same distance from the reflective surface of the rotating mirror shutter as the film plane, on which image plane the viewfinder image is imaged in the exposure pause by transmission optics as a real image on the plane of an image field shutter, and can be viewed through an eyepiece.
In order to allow the contrast scope of a recorded image to be assessed better and to allow scattered light as well as reflected light to be identified more easily, it is known from pages 42 and 43 of the operating instructions for the ARRIFLEX 535 movie camera that a movie camera has to be equipped with contrast filters which can be pivoted by means of a lever into a viewfinder beam path of the movie camera, thus making it possible to vary the quality of the viewing of the recorded image in steps.
JP 10010633 A discloses a viewfinder arrangement for a still-image camera, in which a DMD (Digital Micromirror Device) chip is arranged in the viewfinder beam path and has a large number of two-dimensionally arranged micromirror elements, which comprise micromirrors which are articulated such that they can move and digitally vary the deflection angle when a voltage is applied, that is to say they can be pivoted between two different alignments of the mirror surface. The DMD chip, which is arranged in the viewfinder beam path, is driven by a DMD driver circuit and places either the recorded beams received via an objective or the information emitted from a display in the viewfinder beam path, so that it is possible to view either an object to be recorded or the display information using the viewfinder. The display and the driver circuit which drives the DMD chip are driven by a common CPU.
This known viewfinder system is, however, not suitable for overlaying format indications on the viewfinder image of a movie camera or for superimposing or simultaneous overlaying of recording-specific or camera-specific data in a viewfinder image together with the viewfinder beam path, which is tapped from a recording beam path, since the display information which is overlayed in the viewfinder beam path is input from the display, but is not governed by the position or deflection of the micromirrors.
It is also known for DMD chips to be driven with a changing frequency, so that the gray-scale levels for the light transmission by means of the DMD chip can be varied as a function of the ratio of the switched-on times to the switched-off times, that is to say a brighter gray-scale level is transmitted when the switched-on times are long in comparison to the switched-off times, while darker gray-scale levels are transmitted if the switched-off times are increased in comparison to the switched-on times.
A further problem in the operation of movie cameras is that there is a risk of the introduction of stray light via the eyepiece and the viewfinder beam path into the movie camera and thus into the recording beam path, resulting in undesirable exposure of the movie film, when, for example, the eyepiece is not covered by the cameraman's eye. In order to prevent such inadvertent exposure of the movie film by means of stray light, complex measures are required, which consume space.